Abstract1: Approved Document L2 of the Building Regulations, for the Conservation of Fuel and Power in buildings other than dwellings, asks for building services systems including heating, lighting, mechanical ventilation and air conditioning, to be commissioned. The process involves drawing up a commissioning plan, carrying out commissioning so that the installed systems perform to the designer's specification, and the production of a certificate confirming that the commissioning has been carried out. The four parts are 1 A guide for clients, 2 A guide for designers, 3 A guide for specifiers, 4 A guide for facilities managers.